The present invention relates to computerized tomography (CT) communication, and more particularly to a optical communication system employed in a CT system using electrical energy, light energy, a magnetic field, or thermal energy to change internal reflection conditions within a waveguide to cause a guided wave to be refracted so that high bandwidth data contained therein is radiated from the waveguide and detected by an optical detector within a localized area.
CT systems typically employ a rotating frame or gantry to obtain multiple x-ray images, or views, at different rotational angles. Each set of images is identified as a "slice." A patient or inanimate object is generally positioned in a central opening on the rotating frame on a table, the table being axially movable within the central opening so that the patient may be positioned at various locations enabling respective slices to be obtained at multiple axial positions. Each of the slices obtained is then processed in a computer to produce enhanced images that are useful for diagnoses and inspection.
The rotating frame includes an x-ray source, a detector array and electronics necessary to generate image data for each view. Stationary electronics is employed for processing raw image data. It is necessary to communicate image data between the rotating frame and a stationary frame of the CT system.
The rate of data communication between the stationary and rotating frames is important because it affects the speed at which the images can be processed. It is desirable to obtain image views as fast as possible to reduce patient discomfort and to maximize equipment utilization. In current CT systems, a single view typically comprises about 800 detector channels with a 16 bit representation for each individual detector channel (i.e., 12.8 thousand bits per view), and is typically repeated one thousand times per second, yielding a net data rate of approximately 13 million bits per second (Mbit/sec) for image data alone. Future CT systems capable of simultaneously constructing multiple image slices by employing four, eight, sixteen, or more times as many detector channels, will increase the data bandwidth requirement to the giga bits per second range.
Prior CT systems have employed brushes, slip rings, and radio frequency links for communicating the image data between the rotating frame and a stationary frame. CT systems utilizing brushes and slip rings for communications have generally suffered significant limitations in data transfer rates due to the substantial time required to propagate the signals around the circular slip rings. At the desired data rates, the electrical path length around the rings is an appreciable fraction of the data bit transfer period so that electromagnetic waves propagating around the rings in the opposite direction may arrive at the reception point at substantially different times within the bit transfer period causing signal interference.
Additionally, radio frequency communication links, historically, have not been able to achieve the data transfer rates in the giga-hertz range required of present and future CT systems. Radio frequency links typically operate in the Mega-hertz bandwidth because of radio frequency side band interference and electrical signal propagation limitations within the electronics which generate the radio frequency carrier signals. As such, it is desirable to employ a CT communications link between the stationary electronics and rotating electronics that can operate in the giga-hertz bandwidth so as to facilitate simultaneous image construction using a plurality of detector channels.
It is also desirable to provide a communication link between the stationary frame and the rotating frame which is immune to electromagnetic radiation interference such as is typically produced in a hospital environment by cellular telephones, defibrillating devices, surgical saws, and electrical noise produced by any given CT system.